Traveling wave tube oscillator



Oct. 3, 1961 M. FAVRE 3, 3, 19-

TRAVELING WAVE TUBE OSCILLATOR Filed Jan. 26, 1959 Maurice FA VRE Wr W 9 ATTORNE 3,903,119 WA E E O L R Maurice Eavre, Paris, France, assignor to Compagnie Generale de Telegraphic sans Fil, Paris, France e Eiled Jan. 25,1959, se No. 788,857 Cl ms p i r ty. np i tic Fran b- 8- I 14 Chime .tcl- 31- 2) The present invention relates to a traveling wave oscillator-type electron discharge device and more particularly to a backward wave oscillator having an auxiliary electrode arrangement operative to increase the uniformity and'lehgt-h of life of the attenuation used in such tubes.

The present invention-is concerned with oscillatortubes for ultrahigh-frequency or hyper-frequency waves, generally khow'n finder" the'iianieof -Carcinotrons" (regi'stered' trademark), aridhs concernedespecially with Carcinot rons of M-typeQthatisto those types of tubes in which anelectroh 'heamfemi'ttedby the electron gun moves .perpendicularlytoboth"the electric field and a magnetic field mutually crossed with respect to the electric field in an interaction space comprised between a delay lineand anfelectrode generally referred to, as sole and disposed siseht'ially parallel to the delay line the electric field, beingfe'st ablis hed 'by a diflerencc of potential rendering the delay line'positive with respect to the sole electrode. '4

It is already known in the prior art that in the oscillatoftllbc of is y he ul r bhis irfrequenqv energy is removed at the e d d lthe'dc a'rline adja en th ectron'g'iin ann'tinat; at, the other end or the delay l ne, a portionfo f "the delay line? is evered by an absorbing mlfiil f rmin a i'e c fiatiom' eces ry to impede and prevent s' iich S machinations o ul rah hfrcquency energy atfthis' 'erid,li.e. ,"at the'collector end.

The absorbingmatrials,htilized in connection with the attenuation, are generally I of physical granular structure. Since these materials 'are subjected to the electric field which prevails in the in tract'ion'space, and at the same time are heated by the electronic bombardment, it happens, particularly in case of high voltage tubes, that particles of the attenuating bodies: become loose or detached and produce arcs which are prejudicial to the proper functioning of the tube and to the length of life of the tube. Furthermore, the velue itself of the 3113611112.? tion cannot remain constant under theseconditions with the passage of time.

The present invention has as its object an attenuating system which is, improved and'which is ten d to minate the shortcomings and disadvantages of the tubes in question mentioned hereinaboye.

The presentinvention also has as its object a tube having'a greater attenuation per unit length.

According to, the present invention, a tube of; the type described hereinabove which includes a sole electrode and a delay line having a portion thereof attenuated and a portion thereof nonaattenuated, is. characterized by the fact that a supplementary or auxiliary electrode, elec-. trically insulated from the, sole and placed at the same potential as the'delay line, is disposed in the extension of th'sole in such a manner that'the sole and. the auxiliary'ele'ctrode' tace respectively. the. portions. of. the. delay line which are non attenuatedand which are attenuated respectively,

Owing to such an arrangement the attenuated portion of the delay linejis" not subjected to any electric field.

' Accordinglyfit is an object of the present invention to provide a traveling wave tube oscillator operating by interaction with a baekward space wave which has improved characteristics insofar as the attenuation at'the collector end thereof is concerned.

nitcd States atent ice Another object of :the present invention is the provision of a backward wave oscillator tube which has an increasedlength of life and a greater attenuation characteristic per unit length of the .delay line.

A still further object of the present invention isathe provision of a tube in which arcing due to loose attenua' tion particles is essentially precluded.

A further object of the present invention is the provision of a backwardly oscillator tube, particularly of the M-type in which-the portion of the delay line covered with attenuating material or made of such material is not subjected to any electric field. 7

These and other object features and advantages oft he present invention will beeome more obvious from the following description when taken in connection with the accompanying drawing which shows, for purposes of illustration only, several embodiments in accordance with the present invention, and wherein.

"FIGURE 1 is a longitudinal cross-sectional view of a conventional backward wave oscillator having a delay line-sole arrangement as'known in the prior art,

FIGURE 2 ,is a longitudinal cross-sectional view through backward wave oscillator with a delay line-sole arrangement in accordance with the present invention, and FIGURES 3 and 4 are partial cross-sectional views of modified embodiments of a backward Wave oscillator in aecordance with the present invention. 1

Referring now to the drawing wherein like reference numerals are used throughout the various views to desist nate like parts, and more particularly to FIGURE 1, the tube illustrated therein shows a longitudinal cross-sectional view through an oscillator tube generally known under the trade name of Qarcinotron? The type and operation of such backward wave oscillator is 'inote particularly deseribed in the copending: application S. N'. 281,347, filed April 9, 1952, entitled Backward Flow Traveling Wave Oscillators, by Bernard Epsztein which is assigned to the assignee of the present invention, The delay line. 2T2, shown in FIGURE 2v which is composed of a plurality oi delay elements 2. and Z is disposed essentially parallel to the negative electrode 3 usually referred to as sole within the interior of a vacuum casing or envelope 1. The delay elements. 2', which areusually identicalto the delay elements 2 of the. delay line, are covered, with an attenuating substance: generally indicated in FIGURE 2 in black. An electronernissive cathode 4, heated by a filament 5, faces an auxiliaryelectrode 6. The delay line 2, 2 and the. sole 3 delimit therebetween an interaction space '7 which is.

' closed at the end thereof opposite the cathode 4 by a collector electrodewall 8. The end of the delay line 2. adjacent the cathode 4 is connected with an output con,- nector 9 passing through a glass seal in. A permanent magnet or an electrentagnet, not illustrated in the draw ing, produces, amagnetic field H perpendicular to the. plane. of the FIGURE 1 Whereas, a suitable source ofi voltage 11 enables to carrythedifferent electrodes of the backward wave, oscillator at; the appropriate respective voltages, a part of thisvoltage supply: 11 ElSO'SEFVlIIE; for purposes. of; heating the, filament 5. The. sole 3 may. be connected'tothe; cathode 4, as indicated in; FIGURE 1,,011. may be insulated from, the cathode 4' and. carried: at; apotential difierent therefrom by means of a suitableconz nection (not illustrated).

The tube. so far described'iswell-known, in the prior art; it is known thatin; this type of tube an electron beamlZ, emitted by the cathode 4' and propagating with: in the interaction. space 7; gives rise to oscillations-of ultrahigh-frequency energy by-the process, oh exchange of energy between the beam 12;; and. anegativeor back ward space harmonic of the wave produced in the tube,

the removal of the ultra-high-frequency oscillatory energy taking place by means of the output connection 9.

While the majority of the electrons emitted by the cathode 4 reach the collector wall 8, a relatively large number of electrons deviate from the mean trajectory, parallel to the sole 3, and impinge on the elements of the delay line, particularly on the elements 2 thereof which are covered with attenuating substances. The absorbing materials which form these substances are thus subjected to electron bombardments which are the more intense the higher the voltage used in the tube. On the other hand, the electrostatic fields produced by the high voltages contribute also to the deterioration of the layers in the form of granular material constituting the attenuation. Consequently, particles thereof become detached from the absorbing bodies and produce disturbances in the functioning and operation of the tube while destroying the existing match of the impedances and disarranging the entire attenuation over the full length thereof.

These inconveniences and disadvantages of the prior art are eliminated in the improved tubes according to the present invention, such as represented in the embodiments of FIGURES 2, 3, and 4 in which the same reference numerals designate elements again corresponding to those of FIGURE 1.

The tube according to FIGURE 2 which is improved in accordance with the present invention differs from that of FIGURE 1 by the fact that the sole electrode 3 is relatively shorter therein and does not extend byeond the non-attenuated portion 2 of the delay line. In the extension of the sole 3, but insulated therefrom, is a supplementary or auxiliary electrode 13 forming part of the collector electrode 8 and being so disposed as to face the attenuated portion 2' of the delay line. Since the collector electrode 8 is placed at the same potential as the delay line 2, 2', it is quite obvious that no electric field exists between the attenuated portion 2 of the delay line and the electrode 13 since the latter is nothing but an extension of the collector 8. The original interaction space 7 is therefore divided in FIGURE 2 into two.

parts 7a and 7b respectively to the left, and right of the delay line. The first portion 7a is always the location of the electric field and of a crossed magnetic field Whereas the second portion 7b is so arranged that exclusively a magnetic field exists therein whereas the electric field is zero.

It follows therefrom that the electrons of the electron beam 12 after traversing the interaction space 7a impinge directly on the beginning of the electrode 13 without penetrating therebeyond into the interaction space portion 7b.

Owing to this arrangement in accordance with the present invention it is no longer possible that electrons impinge on the elements 2' of the delay line which carry absorbing substances. Furthermore, the elements 2' of the delay line are no longer subjected to any electrostatic field. The danger of deterioration of the attenuating materials is therefore eliminated with all the inconveniences and disadvantages which result therefrom. Furthermore, the absence of the electron beam within the attenuated zone permits an increase of the attenuation per unit length of the tube by placing within the casing 1, and more particularly within the portion thereof in which the electric field is zero, additional dissipating elements as indicated, for example, in the embodiment of FIGURES 3 and 4 which represent only the portion of the tube comprising the attenuated elements 2' of the delay line.

In the embodiment of FIGURE 3, the wall of the elec trode 13 facing the attenuated elements 2' of' the delay line is also covered by an absorbing substance 14 in such a manner as to increase the attenuation of the portion 7b. Furthermore, the thickness of the electrode 13 is increased thereat, which decreases the interaction space 71) comprised between this electrode 13 and the delay line 2', that is, which in effect decreases the dimension d of FIGURE 3. Additionally, it may be advantageous to choose the dimension of the side d of such value that within the zone 7b, the delay line operates at its cutofi frequency. It is known in fact, that under these conditions, the attenuation per unit length becomes very large and the length of the portion 7b may thereby be considerably reduced. It should also be noted that the increase of the attenuation intervenes for the lowest frequency of the operating band width of the tube and it is precisely at that end of the spectrum that the attenuation normally is of realtively smaller value.

In the modified embodiment of FIGURE 4, the portion 7b of the interaction space without electric field comprises, in addition to the attenuated delay line elements 2, an auxiliary portion of delay line 15, carried at the same potential as the delay line 2, 2' of which it may simply be an extension bent back upon itself.

It is also possible to utilize an attenuation in space by disposing into the zone 7b elements such as plates made of ceramic material, for example, of appropriate form and covered by dissipating material.

While I have shown several embodiments in accordance with the present invention, it is understood that the same is not limited thereto, but is susceptible of many changes and modifications within the spirit and scope of the present invention, and I, therefore, do not wish to be limited to the particular embodiments shown and described herein but intend to cover all such changes and modifications as are encompassed by the scope of the appended claims.

I claim:

1. A microwave oscillator comprising an electron source and a collector electrode defining therebetween a path and interaction space for the electron flow, a wave guiding structure positioned along said interaction space in which there is induced by the electron flow an electromagnetic wave which travels in the direction opposite to that of electron flow, means coupled to said wave guiding structure for abstracting the induced wave, and attenuating means operatively connected with the portion of said wave guiding structure remote from said electron source including means rendering the portion of said interaction space adjacent thereto essentially free from any electric field.

2. A microwave oscillator of the type having crossed electric and magnetic fields comprising an electron source and a collector electrode defining therebetween an interaction space for the electron flow, a wave guiding structure positioned along said interaction space in which there is induced by the electron flow an electromagnetic wave which travels in the direction opposite to that of electron flow, means for producingan electric field in said interaction space, means coupled to said wave guiding structure for abstracting the induced wave, and attenuating means operatively connected with the portion of said wave guiding structure opposite said electron source including means rendering the portion of said interaction space facing said attenuating means essentially free from said electric field.

3. A microwave oscillator of the type having crossed electric and magnetic fields comprising an electron source and a collector electrode defining therebetween a path of electron flow, a wave guiding structure positioned along said path in which therein is induced by the electron flow an electromagnetic wave which travels in the direction opposite to that of electron flow, an auxiliary electrode facing at least a portion of said wave guiding structure and defining therebetween an interaction space, said electric field being established in operation in said interaction space, means coupled to said wave guiding structure for abstracting the induced wave, and attenuating means operatively connected with the portion of said wave guiding structure remote from said electron source includ ing means rendering the portion of said interaction space facing the attenuating means essentially free from said electric field.

4. A backward wave travelling wave oscillator tube including an anode shaped as a delay line having at one of its ends a portion coated with an attenuating substance, a negative sole electrode facing said delay line and defining therewith an electron and wave interaction space, an additional electrode facing said attenuated portion of the delay line, said additional electrode being electrically insulated from said sole and raised to substantially the same potential as said delay line, an electron gun adjacent the other end of said delay line for emitting a beam of electrons, means for producing crossed electric and magnetic fields for propagating said electrons through said interaction space, and ultra-high-firequency output means connected to said delay line near said electron gun.

5. A backward wave travelling wave oscillator tube as claimed in claim 4, wherein said additional electrode is coated with an attenuating substance on the surface thereof facing said delay line.

6. A backward wave travelling wave oscillator tube as claimed in claim 4, further comprising additional absorbing means disposed between said attenuated delay line portion and said additional electrode.

7. A backward wave travelling wave oscillator tube as claimed in claim 4, further comprising an additional attenuated delay line portion between said attenuated delay line portion and said additional electrode.

8. A backward wave travelling wave oscillator as claimed in claim 7, wherein said additional attenuated delay line portion is constituted by delay elements of said anode eifectively bent back upon itself.

9. A backward wave travelling wave oscillator tube including an anode shaped as a delay line having at one of its ends a portion coated with an attenuating substance, a negative sole electrode extending essentially parallel to the non-attenuated portion of said delay line and defining therewith an electron and wave interaction space, an additional electrode substantially in registry with said sole and essentially parallel to said attenuated portion of the delay line, said additional electrode being electrically insulated from said sole and raised to substantially the same potential as said delay line, an electron gun adjacent the other end of said delay line for emitting a beam of electrons, means for producing crossed electric and magnetic fields for propagating said electrons through said interaction space, and ultra-high-frequency output means conneced to said delay line near said electron gun.

10. A backward wave travelling wave oscillator as claimed in claim 9, wherein said additional electrode is essentially smooth.

11. A backward wave travelling wave oscillator as claimed in claim 9, wherein said additional electrode is formed integral with the electrode constituting the col lector of said tube.

12. A backward wave oscillator tube including an anode shaped as a delay line having at one of its ends a portion coated with an attenuating substance, an electron gun adjacent the other end of said delay line for emitting a beam of electrons, a sole electrode having a first plurality with respect to and parallel to said delay line and extending opposite the non-attenuated portion thereof, a second electrode of a plurality opposite to said first plurality and parallel to said delay line and extending opposite the attenuated portion thereof, ultra-high frequency energy transfer means operatively connected with said delay line near said electron gun, and means for producing crossed electric and magnetic fields both of which prevail in the space comprised between said sole electrode and the non-attenuated portion of the delay line while only the magnetic field prevails in the space comprised between said second electrode and the attenuated portion of said delay line for propagating said electrons through the first mentioned of said spaces and essentially preventing propagation thereof through the second one of said spaces.

13. A backward wave oscillator tube including ananode shaped as a delay line having at one of its ends a portion coated with an attenuating substance, an electron gun adjacent the other end of said delay line for emitting a beam of electrons, a negative sole electrode parallel to said delay line and extending opposite the non-attenuated portion thereof, a positive electrode parallel to said delay line and extending opposite the attenuated portion thereof, ultra-high frequency energy transfer means operatively connected to said delay line near said electron gun, and means for producing crossed electric and magnetic fields both of which prevail in the space comprised between said negative sole electrode and the non-attenuated portion of the delay line while only the magnetic field prevails in the space comprised between said positive electrode and the attenuated portion of said delay line for propagating said electrons through the first mentioned of said spaces and essentially preventing propagation thereof through the second one of said spaces.

14. A backward wave oscillator tube according to claim 13, wherein said positive electrode is essentially smooth along the surface thereof facing said attenuated portion.

699,893 Great Britain Nov. 18, 1953 

